Variometer



March 12, 1940. J. P. PUTNAM VARI OMETER Original Filed July 5, 1935 imz -aw GEA- VENTDR: P M

Patented Mar. 12, 1940 PATENT OFFICE 2,193,343 VARIOMETER John P. Putnam, Boston,

Reece Button-Hole Machine Company, Boston,

Mass., a corporation of Maine Mass., assignor to The Original application July 5, 1935, Serial No. 29,866. Divided and this application February 5, 1936,

Serial No. 62,457

2 Claims. (Cl. 171 -242) This invention relates to variometers especially adapted, although not limited, to tuning units for radio receivers of the "all-wave type.

One object of the invention is to provide means for augmenting the rate of progressive increase of the figure of merit of a variometer, i. e., the ratio of the total inductive reactance thereof to its total resistance, over .the greater part of the variometer inductance-range, i. e., the ratio of its maximum to its minimum inductance, and to augment such ratio, which is a maximum at the upper end of said range. This object is effected by providing one of the variometer windings with a core of paramagnetic material such as finely divided iron held together with a binder and compressed into shape under extremely high pressure, said core constituting an open magnetic circuit having constant reluctance for all positions of the rotor winding.

Another object is to provide means for eliminating the noises produced in a radio receiver embodying my improved variometer due to electrical disturbances that result from the relative movement of the variometer rotor in its supporting frame. This object is accomplished by mounting the rotor support member for rotation in an opening formed in the metallic support member by means of an insulating disc.

Various other objects and advantages of my invention will appear in the detailed description of the embodiment thereof illustrated in the accompanying drawing in which Figure 1 is a vertical section of a variometer embodying my invention.

Fig. 2 is a perspective view of one portion of the variometer rotor and its support member.

Fig. 3 is a perspective view of the variometer stator and the support member therefor.

Fig. 4 is a perspective view of the other portion of the variometer rotor and its support member.

In the exempliflcation of the invention shown in the drawing, the portion In of the rotor frame or support member is provided with a spherical interior surface I I in which is mounted one portion of the rotor winding I2. The complementary portion I3 of said support member also is provided with a spherical interior surface It in which is disposed the other portion I5 of said rotor winding. The outer faces of the support members Ill, I3, are provided with registering circular apertures as indicated at I6. The stator windings II, which co-operate with the rotor windings I2, I5, are mounted on the stator support member I8 which has a spherical exterior surface. By means of the gudgeons I9, which are disposed in the bearings formed by the complementary grooves 20, 2|, in the support members I0, I3, respectively, the stator support is disposed in its proper position with respect to the rotor support and isheld in such position .when said members are secured together by screws (not shown) which pass through theregistering holes 22, passing through the same at the corners thereof. The pin 23 rigidly secured to one of said gudgeons and held stationary in any suitable manner may constitute one of the terminals for connecting the variometer windings in circuit. The stator windings I! and the rotor windings I2, I5, may be connected in series or in parallel.

Enclosed within the central bore of the stator support I8 and held in position by the bushing 24 is a core 25 of paramagnetic material'preferably formed by mixing finely divided iron" with a binder and compressing the same into the de 20 sired shape under extremely high pressure, such cores being well-known articles of commerce and requiring no further description.

The rotor support may be mounted for rotation with respect to, the stator support and the wind- 5 ing carried thereby in any suitable manner. In the present instance, it is shown as mounted in a metallic frame member 26 having a circular opening and the particular means employed for mounting the same in said opening is an insulating disc 21 formed of two semi-circular portions integral, respectively, with the parts I0, I3, of the rotor frame. This disc, in the particular embodiment of the invention shown in the drawing, has its bearing in the ball-cage 28 which projects into the circular opening aforesaid in the plate 26, the flange 29 on said cage holding the same in position. The metal. disc 30- secured by screws, one of which is shown at 3|, to the two-part irisulating disc 21 carries the ball-cup 32 which projects into a cavity formed in the wall of the metallic ball-cage and co-operates with the periphery thereof to make a raceway for the anti-friction balls 33. The dial knob 34 is suitably secured to the stud as integral with the disc 45 30 which, as shown, is of smaller diameter than the inside diameter of the ball-cage and does not make rubbing contact therewith.

By mounting the variometer. rotor support member for rotation in the metallic frame mem- 50 her 26 by means of said insulating discs, I eliminate the grinding noises that would be produced by a radio receiver embodying my variometer if said discs were metallic, such noises being caused by electrical disturbances due to the relative 55 movement of two contacting, conducting members only one of which is grounded.

By providing the variometer with a core having greater permeability than air, the magnetic field is concentrated and leakage reduced, thus insuring a greater flux linkage between the coils. Another result obtained by using a magnetic core is that the figure of merit of the variometer, that is, the ratio of the total inductive reactance thereof to its total resistance, known as the Q of the variometer, is increased over thegreater part of the variometer inductance-range or the ratio of its maximum to its minimum inductance. I have ascertained that the use of such core in a variometer is practically without eifect on the Q thereof at and near the lower end of its inductive range where the coils are in or near the position of maximum opposition and minimum inductance.

The minimum inductance of a variometer is equal to the sum of the self inductances of the rotor and stator coils minus twice the mutual inductance thereof. As the rotor is turned toward the position of maximum assistance and maximum inductance, such maximum inductance being equal to the sum of the self inductances of the rotor and stator coils plus twice the mutual inductance thereof, the Q of the variometer is .progressively increased and is a maximum at the upper end of the inductance range.

I have ascertained experimentally that the use of said core results in a marked increase in the variometer inductance range, i. e., the ratio of the maximum inductance of the variometer to the minimum inductance therefor.

In some of the tuning elements of the kind described in my application Serial No. 29,866, filed July 5, 1935, which has matured into Patent Number 2,066,945, dated January 5, 1937, of which this application is a division, the inductance range of the variometer that forms the subject matter of the present application is 10:1 such ratio being specified herein merely by way of example and not as a limitation, and this relatively high inductance range is-an important factor in the elimination of the large number of tuning elements heretofore found necessary in each tuning unit of an all-wave radio receiver and the complex multi-contact switching member required for the stator gudgeons and the other end to the A rotor support member. The two portions of the stator winding are connected electrically to the gudgeons l9 and by means of said hair spring the rotor and stator windings are conductively connected. It will be understood of course that any other suitable means may be employed for connecting the variometer windings to each other,-

either in series or in parallel and to the circuit in which the variometer is used.

The ball-cage 28, in addition to its usual function, serves as a shield to screen the variometer from electrical forces that otherwise would pass through the circular opening in the metallic frame member 26 within which the insulating disc 2'! is disposed.

Having thus disclosed as illustrative embodiment of my invention without however limiting the same thereto, what I claim and desire to secure by Letters Patent is:

1. A variometer having a rotor and a stator comprising windings, support members for said windings, a metallic frame member having a circular opening, and means for mounting the support member of the rotor windings for rotation in said frame member, said means comprising a disc of insulating material secured to said support member of the rotor windings and disposed in said circular opening.

2. A variometer having a rotor and a stator comprising windings, support members for said windings, a metallic frame member having a circular ope n and means for mounting the support member ofthe rotor windings for rotation in said frame member, said means comprising a disc of insulating material secured to said support member of the rotor windings and disposed in said circular opening, and a metallic shielding member arranged adjacent to said circular opening.

JOHN P. PU'INAM. 

